1. Field of the Invention
The present invention relates to a cross member arranged as a framework structure in the width direction of a vehicle and a manufacturing method for the cross member.
2. Description of Related Art
A cross member, which is arranged on the backside of an instrument panel so as to extend in the width direction of the vehicle, has both ends fixed to side framework structures of the vehicle. The cross member performs a role as a framework structure in the width direction of the vehicle and another role as a supporting member for various components, for example, instrument panel, column shaft, air bag, etc. Japanese Patent Application Laid-open (heisei) No. 8-282333 discloses this kind of cross member which is shown in FIGS. 1 and 2.
In FIGS. 1 and 2, the cross member 50 includes a main frame 51 extending in the width direction of the vehicle and a pair of brackets 52 fixed to appropriate parts (e.g. both ends) of the main frame 51, in one body. The main frame 51 is made of fiber reinforced thermosetting resin, while the brackets 52 are made of fiber reinforced thermoplastic resin. The main frame 51 includes a frame body 51a having a hollow part 53 defined therein, an inner layer 51b arranged inside of the body 51 and an outer layer 51c arranged outside of the body 51. The frame body 51a is made of fiber reinforced thermosetting resin. The inside and outside layers 51b, 51c are made of fiber reinforced thermoplastic resin, which is similar to that of the bracket 52. That is, in the prior art, since the cross member 50 is made from resinous material and the hollow part 53 of the main frame 51 is used as air-conditioning duct, there have been accomplished weight saving, reduction in number of components, cost saving, reduction in number of assembling steps, space saving, etc.
In the above-mentioned cross member 50, however, it cannot afford sufficient strength to the member's part that is required to have high strength in comparison with the other parts. For example, in case of the cross member 50 arranged on the backside of an instrument panel, the member's part supporting a column shaft is required to have high strength particularly.
Additionally, since the main frame 51 and the brackets 52 are formed by different kinds of resinous materials, a problem of deteriorated recycling efficiency arises.
Meanwhile, the conventional cross member has been provided by injecting molten resin to the circumference of a main frame (see publications of Japanese Patent Application Laid-open No. 2000-220598 and Japanese Patent No. 3219407). However, it is noted that the cross member made by these molding methods does not always exhibit high strength. Additionally, there is the possibility of torsion and flexure in the cross member.